This invention relates to a television receiver including a teletext processor including character generator means and teletext page memory means for receiving, decoding and displaying teletext data, means for generating an on-screen message display, the on-screen message display generating means including a further memory means storing the required data for the on-screen message display, and microprocessor means for controlling the teletext processor and the on-screen message display generating means.
Such a television receiver is disclosed in U.S. Pat. No. 4633297. In the receiver disclosed in this document the on-screen display messages are stored in a read-only memory (ROM) which is read out under control of a microprocessor into the television page memory. Appropriate memory timing and control arrangements select whether the teletext data being received or the stored pages from the on-screen display ROM are written into selected locations of the teletext page memory. Data from the teletext page memory is then fed to a character generator which provides the signal for driving the display device. This arrangement enables on-screen display messages to be overlayed on the teletext data merely by writing on-screen display message data from the ROM into the teletext page memory at the appropriate locations. A disadvantage of the receiver disclosed in U.S. Pat. No. 4,633,297 is that when the on-screen display message is deleted, it will take an indeterminate time for the teletext data to be read into the locations of the memory which had held the on-screen display data, the time depending on the position within the transmitting cycle of the teletext information when the on-screen display message is deleted.